Lead


Lay summary
Recently we presented a new model based on a multi-determinantal description of the multiplet fine structure of the whole ligand field manifold. The key feature of this approach is the explicit treatment of near degeneracy correlation using ad hoc Configuration Interaction within the ac-tive space of Kohn-Sham orbitals with dominant d- or f-character. The calculation of the CI-matrices is based on a symmetry decomposition and/or on a ligand field analysis of the ener-gies of all single determinants calculated according to Density Functional Theory for frozen KS-orbitals corresponding to the averaged configuration, eventually with fractional occupations, of the d- or f-orbitals. This procedure yields multiplet energies with an accuracy of a few hundred wave numbers and fine structure splitting accurate to less than a tenth of this amount. The calculation yields the energies of all single determinants within the whole LF-manifold is per-formed. These energies are then used to estimate all the Racah-, LF- and Spin-Orbit-parameters needed in a conventional LF-calculation. The results of this first-principle predicti-on are in good agreement with the experimental observations. The model has been validated for molecules with open d- and f-shells involving properties like e.g. Multiplet Structure and Fine Structure, Magnetic Exchange Coupling, Zeeman Splitting, Hyper-Fine Splitting, Zero Field Splitting, Shielding Constants, etc. …